A customer called us last year, frustrated. They had designed a handheld scanner with 160g domes, the standard "good feel" force for consumer electronics. But the scanner was for warehouse workers wearing thick work gloves. The 160g dome felt like nothing through the glove. Workers were pressing each button twice, trying to confirm the click, and the scanner was registering double entries. They switched to 250g domes, and the problem went away.
This is the most common mistake we see in metal dome selection: picking a force value based on convention, not on the actual use case. The "standard" 160g dome works great for a phone or a TV remote. It does not work for a gloved finger, a safety interlock, or a button that must not be pressed by accident.
Here is how we help customers pick the right actuation force.
What actuation force actually means
The actuation force of a metal dome is the peak force required to snap the dome from its curved position to its flat position. It is measured in grams (g) or Newtons (N), where 100g = about 1N. The return force is the force the dome exerts when it snaps back, which is typically 30-40% of the actuation force.
The standard dome sizes we stock are:
6mm round dome - 100g, 160g, 250g
8mm round dome - 160g, 250g, 300g
12mm four-legged dome - 250g, 300g, 400g
20mm cross dome - 400g, 500g, 600g
We can also custom-tune the force to ±10g of any target value, by adjusting the die geometry and the material thickness. The most common custom request is 180g or 220g - halfway between the standard values, for a product that needs a slightly firmer feel than the standard 160g but not as heavy as 250g.
Force gauge test fixture measuring actuation force on a sample dome.
Factors that drive force selection
When we ask a customer "what force do you need?", we always follow up with three questions.
Who is pressing the button, and how? Bare fingers on a consumer product: 100-160g. Gloved fingers in industrial or medical settings: 250-300g. Foot switches or heavy machinery: 400-600g. A light touch for a user sitting at a desk is a different design than a button a worker in winter gloves has to operate.
How often is the button pressed? A button pressed once per shift, like a safety override, can be heavy - 300-400g. A button pressed hundreds of times per day, like a scanner trigger, should be lighter - 100-160g - to avoid finger fatigue. We have customers who switched from 160g to 120g for a daily-use keypad, and their users reported 30% less fatigue at the end of the shift.
What happens if the button is pressed by accident? If an accidental press is harmless (like a volume button), 100g is fine. If it is dangerous (like a brake release or a weapon safety), 400g or more is appropriate. The force should be high enough that a bump, a vibration, or a resting hand does not trigger it.
Four-legged stainless steel domes in various actuation forces for different applications.
How the dome size affects feel
Force is not the only factor. The size of the dome changes the feel, even at the same force. A 6mm dome at 160g feels sharper and more precise than a 12mm dome at 160g. The smaller dome has a shorter travel distance (about 0.1mm vs 0.2mm for the 12mm), and the snap is more abrupt.
For a silicone button application, the silicone boot adds its own compression force on top of the dome. A 160g dome under a 50g silicone boot feels like a 210g button. We always recommend accounting for the boot force when specifying the dome. If you want the final button to feel like 200g, and the boot adds 50g, specify a 150g dome.
Common mistakes we see
The first mistake is copying a competitor's spec. Just because your competitor uses 160g domes does not mean your product needs 160g. If your product has a different use case, a different boot material, or a different user demographic, the right force is different.
The second mistake is over-designing for safety. A customer once specified 500g domes for a consumer TV remote. We told them it would feel like pressing a brick, but they insisted. After two months of user testing, they came back and switched to 160g. A button that is too hard to press is as bad as one that is too easy.
The third mistake is not testing with real users. We provide free sample kits with domes in all standard forces. We recommend 3-5 prototype units, each with a different force, and let your actual users press them. The engineering team's opinion is not the same as the user's opinion. We have had engineers say "this 250g dome feels perfect," while the end users said "it feels like a rock."
If you are designing a dome sheet array or a membrane switch panel and you are not sure which force to specify, send us your application details and we will recommend a starting point. We can also ship a free sample kit so you can feel the difference for yourself before you commit to a production order.
- John Smith, Senior Application Engineer, Shanyo
